In the manufacturing processes of an electronic part assembly in which an electronic part, such as a semiconductor chip, a resistor, a thermistor or a capacitor, is mounted on a wiring substrate, resin encapsulation is performed in order to protect the mounted electronic part from the outside. See Japanese Laid-Open Patent Application No. 2003-309134, Japanese Patent No. 3343131, and Japanese Patent No. 2745207.
Generally, a resin ejection nozzle which has the cross-section in circular formation is used.
As disclosed in Japanese Laid-Open Patent Application No. 2003-309134, a method of applying encapsulation resin to a predetermined encapsulation area is known. When applying encapsulation resin to an encapsulation area of a wiring substrate, a resin ejection nozzle for applying a fluid-state encapsulation resin is used, and the resin ejection nozzle is scanned on the wiring substrate while the encapsulation resin is ejected from the resin ejection nozzle.
However, in the above-mentioned method, repetitive movement of the resin ejection nozzle over the encapsulation area must be carried out so that the resin is applied, and there is a problem that a long time is required for the resin application. Moreover, the mechanism for controlling the movement of the resin ejection nozzle or the wiring substrate is complicated, and it causes the manufacturing cost to be raised.
A conceivable method for solving the above problem may be a method of applying encapsulation resin using a resin ejection nozzle which is provided with a slotted ejection hole having a longitudinal direction perpendicular to the direction of movement of the nozzle, and the method using the resin ejection nozzle can apply encapsulation resin to a wide area.
However, when the above-mentioned resin ejection nozzle is used, the encapsulation resin ejected from the nozzle contacts the side surface of the electronic part as a whole simultaneously which is perpendicular to the direction of movement of the nozzle. After the resin application, air bubbles may be included in the part of the encapsulation resin near the electronic part, and the appearance becomes poor due to the air bubbles. And when the encapsulation resin is heated, the air bubbles will be expanded and a void will occur there. This causes the reliability to become poor.